1. Field of the Invention
This invention relates to an information recording medium. Also, this invention relates to a method and an apparatus for recording information on a recording medium. In addition, this invention relates to a method and an apparatus for reproducing information from a recording medium.
2. Description of the Related Art
A DVD (digital versatile disc) family contains a DVD-Video and a DVD-RW. Here, DVD-RW is short for DVD-Rewritable.
The DVD-Video is designed for a playback purpose (a reproduction purpose) only. In general, the DVD-Video stores main information, and copyright information corresponding to the main information. For example, the copyright information is designed to prevent the contents of the main information from being illegally copied. According to a CSS (a contents scramble system), the copyright information is recorded on a given area of the disc, that is, an area of the disc which is assigned to information related to copyright protection such as information of a CSS key.
A DVD-Video player operates as follows. First, the player reads out information of a CSS key from a disc. When the information of the CSS key is correct, the player is permitted to reproduce the contents of main information from the disc. Otherwise, the player is inhibited form reproducing the contents of the main information. Thus, the CSS key functions to prevent the contents of the main information from being illegally copied.
It is assumed that a DVD recording system illegally records DVD-Video contents information and corresponding CSS-key information on a disc. In this case, since the correct CSS-key information is present in the disc, a DVD-Video player can reproduce the DVD-Video contents information. Thus, in this case, it is difficult to protect copyright on the DVD-Video contents information.
The DVD family also contains a DVD-R (a DVD-Recordable). Information can be recorded on the DVD-R only once. It is conceivable that before the shipment of a virgin DVD-R from a factory, the disc is physically processed to record a special code signal other than a signal of a CSS key on a given area of the disc which corresponds to a copyright information area of a DVD-Video. In this case, it is difficult to write information of a CSS key over the given area of the DVD-R after the shipment thereof from the factory. It is assumed that a DVD recording system illegally records DVD-Video contents information on such a DVD-R. CSS-key information corresponding to the DVD-Video contents information is absent from the DVD-R since it is difficult to record the CSS-key information on the disc. Accordingly, in this case, a DVD-Video player can not reproduce the DVD-contents information from the disc. Thus, it is possible to protect copyright on the DVD-Video contents information.
The DVD-RW has the feature that information can be repetitively recorded thereon a plurality of times. An explanation is now given of the case where before the shipment of a virgin DVD-RW from a factory, a special code signal other than a signal of a CSS key is recorded on a given area of the disc which corresponds to a copyright information area of a DVD-Video. Even in this case, it is possible for a DVD recording system to illegally record DVD-Video contents information and corresponding CSS-key information on the DVD-RW after the shipment thereof from the factory. Since the correct CSS-key information is present in the disc, a DVD-Video player can reproduce the DVD-Video contents information therefrom. Thus, in this case, it is difficult to protect copyright on the DVD-Video contents information.
Regarding a DVD-RW or a similar rewritable disc storing DVD-contents information permitted to be copied, it is desirable that the DVD-contents information can be reproduced from the disc. Also, in some cases, it is desirable that the DVD-contents information can be copied.
An optical disc conforming to the RTR (real-time recording) standards is incompatible with a DVD-Video. Regarding an RTR disc storing main information and copyright information, it is desirable to control the copying (the recording and the reproduction) of the main information in accordance with the contents of the copyright information.